Primary Research Of Molecular System Category In Seven Cladocera Species

Daphnia and Moina can be categorized as Arthropoda, Crustacea, Branchiopoda,Diplostraca, Cladocera, Chydoroidea, which belongs to Daphniidae and Moinidae,respectively. Daphnia and Moina are dominant species of Cladocera in many lakes inChina. Identification of some species is uncertain or even wrong due to their highmorphology similarity among close species. This paper examined the systematicclassification of seven cladoceran species by the method of molecular marker andmeasuring sequence, and corrected some classified errors in some species.In order to examine the systematic classification of four Daphnia species, D.carinata, D. hyalina, D. pulex and D. magna recorded previously, genomic DNA of fourDaphnia species were extracted through the kit method. PCR was used to amplify partialsequences of16S rDNA，CO I and ITS2sequences of four Daphnia species byemploying specific primers, and same sequence with higher matching rate of eachDaphnia species from the GenBank was analyzed. Based on16S rDNA and CO Isequences, the average interspecific similarity rate of four Daphnia species wasrespectively85.25%，80.67%and47.9%, and the content of A+T was obviously higherthan G+C in mitochondrial gene. Based on CO I gene, the similarity of D. carinata fromLake Chaohu and D. similoides (AB549199) from the GenBank was99%, and thedivergence rate was0.4-0.9%. In terms of16S rDNA, CO I or ITS2gene, D. hyalinafrom Lake Chaohu was more close to D. galeata from the GenBank. Main branches ofboth NJ tree and Bayes tree were similar. The results indicated that D. carinata and D.similoides was the same species, and D. hyalina should belong to D. galeata. Due to theabsence of nuclear gene analysis, the classification status of Daphnia species in LakeChaohu need be further investigated.In order to examine the systematic classification of three Moina species, M. irrasa, M. brachiata and M. micrura recorded previously, genomic DNA of three Moina specieswere extracted through the kit method. PCR was used to amplify partial sequences of16SrDNA of three Moina species by employing specific primers, and same sequence withhigher matching rate of each Moina species from the GenBank was analyzed. Based on16S rDNA, the average interspecific similarity rate among three Moina species was88.75%, and the content of A+T was obviously higher than G+C. The similarity of M. irrasa inthis study and M. macrocopa from the GenBank was99%, and the divergence rate was0.5%, within a range of same species. The similarity of M. brachiata from Lake Chaohuand M. brachiata from the GenBank was relatively low (89%), and the divergence ratewas14%, within a interspecific divergence level. The both NJ tree and Bayes tree basedon16S rDNA did also support these results. The results indicated that M. irrasa in thisstudy and M. macrocopa from the GenBank might be the same species, and M. brachiatafrom Lake Chaohu and the GenBank had reached the interspecific divergence level. Dueto the absence of morphology and other gene analysis, the classification status of Moinaspecies in this study mentioned need be further investigated.